When using a long object to be printed in a digital printer, a roll on which the long object to be printed is wound is used. In this case, the object to be printed should be transferred to a lower side of a head of the digital printer at a constant velocity, while applying a constant tension thereto.
To transfer an object to be printed for digital printing in the related art, as illustrated in FIG. 1, there is a digital printer 100 including a first transfer roll 110 and a second transfer roll 112 which are disposed on a front and rear about a head unit 102 thereof, respectively, a first auxiliary roll 108 disposed upstream from the first transfer roll 110, and a second auxiliary roll 114 disposed downstream from the second transfer roll 112. Herein, the first auxiliary roll 108 and the second auxiliary roll 114 are positioned below the first transfer roll 110 and second transfer roll 112, respectively. As a result, since a contact area of an object 10 to be printed with the first transfer roll 110 and second transfer roll 112 is increased, it is possible to stably transfer the object 10 to be printed with an increased frictional force.
In addition, a supply roll 104 is disposed upstream from the first transfer roll 110 for supplying the object 10 to be printed to the first transfer roll 110, and a rewinding roll 118 is disposed downstream from the second transfer roll 112 for rewinding and collecting the object 10 with an image printed thereon.
Herein, a process for mounting the object 10 to be printed in the digital printer 100 having the above-described configuration will be described with reference to FIG. 2. First, one end of the object 10 to be printed being supplied from the supply roll 104 is unwound, and sequentially passed through the first auxiliary roll 108, the first transfer roll 110, the second transfer roll 112, and the second auxiliary roll 114. Then, the one end of the object 10 to be printed is fixed to the rewinding roll 118.
However, in the related art, even though the digital printer 100 has a large size, it is very cumbersome for the operator to manually pass the object 10 to be printed through the first transfer roll 110 via the first auxiliary roll 108, the second transfer roll 112, and the rewinding roll 118 via the second auxiliary roll 114. Further, since the object 10 to be printed is made of a thin material such as paper or a film, or the like, when a force is not uniformly applied thereto in a width direction thereof, the object to be printed may be torn or strained. In addition, if the object 10 to be printed is not accurately mounted on the first transfer roll 110 and second transfer roll 112, the straightness thereof is varied, and thereby printing on the object to be printed may be deteriorated and wrinkles may be formed thereon. Therefore, there may be a problem that the wrinkles generated on the object contact a lower surface of the head unit 102 of the digital printer 100 to cause damage in a head (not illustrated).